I have a Note 10+, two Linux computers, and an ancient Mac which I seldom use. The Linux computers run 1.12.1, the Mac just upgraded itself to 1.13.0.
The Android was running syncthing-fork, unknown version, probably the latest. After the upgrade to Android 11, I could not get syncthing-fork to get past the settings screen where it needs “all files” permission, so I could not clear its setting to start on power-on, nor could I check the current settings. I had to uninstall it so it would not start on power-on.
Syncthing not-fork runs fine … but I had to re-introduce the other three computers, and Syncthing did not recognize their real names until the sync folder was recognized.
The worst problem was trying to get it to recognize that sync folder. It defaulted to the SD card; I have a data folder in main memory, /Sync ("//STORAGE/EMULATED/0", as it says, beginning with two forward slashes), and while its directory picker lets me choose that dir (USE THIS FOLDER), and I agree to “Allow Syncthing to access files in Sync”), I get an error message paraphrased as “Sorry, cannot use that directory. Please use internal or external storage”. I think its complaint really means “I don’t like symlinks”, because if I instead choose “/storage/emulated/0/Sync”, it recognizes the folder and (strange to me) the two Linux computers’ real names.
I also had the same brain fart as has tripped me up before, where I did not change the folder key to “default”. Veterans will remember my idiocy over that from before, possibly twice, but this time I remembered before complaining on the forum.
If I were doing this over again, I would switch from syncthing-fork to syncthing BEFORE the Android 11 upgrade, to isolate those problems from any Android 11 problems.
Hmmmm … ETA that now the phone thinks all three computers are out of sync; 85% or so. I do backup my “master” sync computer, for just this reason; I’ll let these strange syncs finish, then compare to my backup and see what it thinks changed. So far it’s just one video and .stfolder, which now has a “(1)” conflict file.